Spectrophotometric determination of biologically active thiols with eosin, silver(I) and adenine.

A simple and highly sensitive spectrophotometric method for the determination of biologically active thiols based on the fading of eosin-silver(I)-adenine ternary complex was established. In the determination of 6-mercaptopurine (MP), Beer's law was obeyed in the range 0.02-0.30 microg ml(-1), with an effective molar absorptivity at 562 nm and the relative standard deviation being 3.5 x 10(5) dm3 mol(-1) cm(-1) and 0.72% (n = 5). Analytical data for various biologically active thiols were determined with the proposed method. This method is about 5-10 times more sensitive than the conventional spectrophotometric methods. A compound having a disulfide bond (-S-S-), such as cystine, could also be determined by the conversion of disulfides to free thiols with the sulfite ion. The procedure was successfully applied to assays of various biologically active thiols in actual medicines.     

On the mechanism of proton transfer reactions in the excited hydrogen bonded complexes

The results of systematic experimental studies on the hydrogen bonding and proton transfer reactions between excited naphthol molecule and aliphatic amine molecule in nonhydroxylic solvents are described and interpreted.The mechanism of the proton transfer process is discussed on the basis of the - interaction in the hydroxy group of naphthol and the charge transfer interaction between the proton acceptor and the donor in the excited electronic state.

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Zusammenfassung Die Ergebnisse systematischer experimenteller Untersuchungen über Wasserstoffbrückenbindung und Protonenaustausch zwischen angeregten Naphtholmolekülen und aliphatischen Aminen werden beschrieben und interpretiert. Es werden Lösungsmittel ohne Hydroxylgruppen benutzt.Der Mechanismus der Protonenaustauschreaktion wird diskutiert auf der Basis einer --Wechselwirkung in der Hydroxylgruppe des Naphtholmoleküls und einer charge-transfer-Wechselwirkung zwischen Protonen-Akzeptor und -Donor. Dabei befindet sich der Donor in einem angeregten Elektronenzustand.

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Résumé Les résultats d'études systématiques expérimentales sur la liaison hydrogène et les réactions de transfert de proton entre des molécules de naphtol excitées et des amines aliphatiques sont décrits et interprétés. Des solvants non-hydroxyliques sont employés.Le mécanisme du transfert de proton est discuté sur base d'une interréaction - dans la groupe hydroxyle du naphtol et d'un transfert de charge entre l'accepteur et le donneur du proton, le donneur étant en état excité.

     

Laurencenyne,a plausible precursor of various nonterpenoid C15-compounds,and neolaurencenyne from the red alga laurencia okamurai

Structural elucidation of two new acetylenic polyenes, laurencenyne $\text{5}$ and neolaurencenyne $\text{6}$ isolated from $\text{Laurencia okamurai}$, together with their syntheses, was achieved, suggesting that laurencenyne $\text{5}$ was a possible precursor of various nonterpenoid C₁₅-compounds in the marine red algae of the genus $\text{Laurencia}$.     

CFD computations of NAL experimental airplane with rocket booster using overset unstructured grids

Flows around the NAL jet‐powered experimental airplane with a small rocket booster under the fuselage are computed by solving the Euler equations using the overset unstructured grid method. The main objective of the present study is to evaluate the effect of a small rocket booster, which accelerates the airplane to supersonic speed, on the aerodynamic performance of the airplane during the ascent flight and the booster separation. Two unstructured meshes, one for the airplane and one for the booster, overlap. For the accurate separation simulation, the two bodies are in contact at first, and then the booster mesh is contact mesh is moved relative to the airplane mesh to evaluate flow interactions between two bodies. Copyright © 2005 John Wiley & Sons, Ltd.     

Origin of the color of π‐conjugated columnar polymers: Poly(p‐n‐octylthiophenyl)acetylene prepared using a [Rh(norbornadiene)Cl]2 catalyst

Highly stereospecific polymerization of a novel sulfur containing aromatic acetylenes, that is, (p‐n‐octylthiophenyl)acetylene (pOctSPA), was successfully performed using the Rh complex, [Rh(norbornadiene)Cl]₂‐TEA, catalyst in the presence of various solvents under mild conditions. The resulting polymers were characterized in detail by ¹H NMR, ESR, laser Raman, diffuse reflective UV‐Vis (DRUV‐Vis), and wide angle X‐ray diffraction methods. The data showed that the resulting polymers bear cis‐transoid form, which can induce the cis‐to‐trans isomerization when the cis polymers are subjected to pressure at room temperature under vacuum, breaking rotationally the cis C?C bonds in the main‐chain giving two kinds of π‐radicals, the so‐called cis radical and trans radical as the origin of a polymer magnet like a novel spin glass material. Further, the resulting cis poly(acetylene)s were found to have a helical main‐chain, which is packed in pseudohexagonal crystal called π‐conjugated columnar or nano π‐conjugated columnar as a novel color controllable material. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2836–2850, 2005     

Local concentration of gel phase domains in supported lipid bilayers under light irradiation in binary mixture of phospholipids doped with dyes for photoinduced activation

Recently, lipid bilayers supported on solid substrates are considered to offer potential as biological devices utilizing biological membranes and membrane proteins. In particular, artificially patterned supported bilayers hold great promise for the development of biological devices. In this study, we show control of the formation and location of phase-separated domain structures by light irradiation for gel phase and liquid-crystalline phase separation structures in a DMPC-DOPC binary lipid bilayer tagged with dye molecules on SiO2/Si substrates. Upon light irradiation, the gel phase domain structures disappeared from the phase-separated bilayers. This disappearance indicates that the light irradiation causes a local increase in the temperature of the lipid bilayer. In this disappearance phenomenon, the photoinduced activation of dye lipids, e.g. fluorescent lipids, is considered to play an important role, since the same phenomenon does not occur in lipid bilayers that have a low concentration of dye lipids. Thus, the local increase in temperature is propagated by light absorption of the dye lipid and subsequent photoinduced activation of nonradiative molecular vibrations. Subsequent interruption of the photoinduced activation for molecular motion allowed the gel phase domain structures to precipitate and grow again. Moreover, the domain area fraction remaining after the photoinduced activation was higher than that before the photoinduced activation. This result indicates that the local increase in temperature propagated by dye-excitation enhances formation of the gel phase domains. By utilizing this phenomenon, we could preferentially induce formation of domain structures within the light-irradiated regions. This technique could be the basis for a new patterning technique based on domain structures. Moreover, these domain structure patterns can be eliminated by increasing the temperature, allowing rewritable patterning.